Wave translating device



Dec. 29, 1936. A. l. ABRAHAMS 2,066,133 4 4 WAVE TRANSLATING' DEVICEFiled April 28, 1933 1 5- F a. E a6 23 it 2% L 22 I I [T 4- 14 i4 k 2221 ml 16 5 5? 1:

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ATTORNEY Patented Dec. 29, 1936 UNITED ES "PATENT OFFICE.

WAVE TRANSLATING DEVICE Alexander I. Abrahams, New York, N. Y.

Application April 28, 1933, Serial No. 668,335

6 Claims. (01. 1i9 138) v This invention relates to wave translatingdevices, and with particularity to a device for translating sound wavesinto electric waves and vice versa.

The invention has for its principal object to provide an improved formof wave translating device employing a ribbon like vibratory translatingelement.

A feature of the invention relates to an improved type of microphone.

A further feature relates to an improved form of wave vibratory elementsuitable for use in wave translating devices such as microphones,reproducers or the like.

A still further feature relates to the novel organization, arrangementand relative location of parts which go to make upa simple and highlyefficient wave translating device.

Other features and advantages not specifically enumerated will beapparent after a consideration of the following detail descriptions andthe appended claims.

Referring to the drawing,

Fig. 1 is a front view of a device according to the invention;

Fig. 2 is a right hand elevational view, partly I in section of thedevice of Fig. 1;

Fig. 3 is a partial top plan View of the device of Fig. 1 with the coverand housing removed;

Fig. 4 is a partial sectional view of Fig. 2 taken along the line 4--4thereof Y Fig; 5 is a sectional view of Fig. 3 taken along the line 5-5thereof; and

-Figs. 6 and '7 show modified formed in the vibratory member.

Referring more particularly to the drawing there is shown a rectangularframe member I having flanges 2 and 3. Each of the flanges 2 and 3 isprovided with a recess 4 to receive an insulating strip 5. The-strips 5are attached to the flanges 2 and 3 by suitable screws 6. Mounted oneach of the insulator strips 5 is a metallic strip 1 which is fastenedthereto by means of screws 8. The metallic strips I serve to clamp theends of the vibratory member 9 against the associated insulator members5. As shown in the drawing, the member 9 is preferably in the form of ametallic ribbon of thin material such as aluminum, dur-alumin or thelike. In order to stiffen the member 9 longitudinally to enable it tovibrate in a piston like manner the said strip is provided with alongitudinal embossed rib I 0. To further facilitate the vibration ofthe member 9 in a piston like manner the ends of said member may beprovided with transverse embossings H. While the drawing shows themember I0 consisting of a single recess, it will be understood that theinvention contemplates the provision of a series of separatelongitudinal recesses as desired. It is of course apparent that forms ofribs the rib I!) need not be straight but can have other configurationsas shown at H] and Win Figs. 6 and 7. Similarly, while the drawing showsa single transverse recess, at each end of the ribbon member, it will beunderstood that a plurality of these ribs may be provided at each end toincrease the flexibility of the said member, as shown in Fig. 6. Inaddition the transverse ribs whether used singly or in multiple mayextend to the edges of member 9 as shown in Figs. 6 and '7 at H It willalso be understood that other'well known expedients for rendering theends of the ribbon flexible may be employed. If desired the member 9 mayhave its opposite ends clamped be; tween the members 5 and 1, so as tomaintain the said member 9 ma state of tension, although this is notabsolutely necessary so long as the said member 9 is actively movingthroughout the greater portion of its length'in a piston like manner,that is with its substantial entire area moving uniformly for a givenunit of force impressed thereon. For the purpose of conducting currentthrough the member 9 there is provided a lead-in wire l2 which isfastened by means of screw 8 and therefore contacts with the lower endof the member 9. Another lead-in wirel3 connects with the upper end ofthe member 9. By means of these wires I2 and I3 therefore externalconnections can be made to the ribbon member 9. p

Attached to the front face of the member l are a pair of ple pieces l4,I5. As shown more clearly in Figs. 2 and 4 these pole pieces arein theform of flat meta-l members of iron or other magnetic material, and areheld in place by means of screws 16 soas' to define a longitudinalmagnetic gap between their opposed edges, in which gap is situated themember 9. It'will be understood of course that the member] I carrying,the pole pieces l4 and I5 is of non-magnetic material such as aluminumor the like. 7

As will be apparent from the drawing the gap defined by the pole piecesis slightly wider than the widt'h of the member 9 so as to enablethesaid member 9 to vibrate without contacting with the surface of thepoles. Situated in the rear of the member 9 is a rigidstrip ll ofnon-magnetic material such as brass or the like. The strip i1 is carriedby a pair of screws l8 and I9 which are threaded into the flangeportions 2 of the member I. By means of the screws [8 therely in Fig. 4.The magnets and 2| may be held firmly in position by means of screws 22passing through the wall of the member I. Preferably,

although not necessarily, the space defined by the U-shaped magnets isprovided with a filling of a non-resonant material such as cotton, woolor the like, as indicated by the numeral 23. As

Will be apparent from Fig. 4, the damping plate I1 is of slightly lessWidth than the member 9 so as to allow egress of air from theback of themember 9 into the space defined by the magnets. However, because of thefilling material 23 the air in this space is prevented from resonatingat any frequency within the useful range of the device.

For the purpose of enclosing the above as- V sembly there isprovidedacylindrical cup shaped .spondingly threaded cap member 26.

out its effective length.

housing 24 of metal or other suitable material having a threaded flange25 to receive a corre- The cap member 26 is provided with a series offour locks Zlwhich engage the respective corners 28 of the member I toclamp the above described assembly firmly in position between the capand the flange 25. If desired theannular opening in the cap as amicrophone the sounds or other waves to be translated into correspondingcurrerits'impinge upon the member 9, causing it to vibratethrough-Sincethis member is situated in an intense and concentrated magneticfield defined by the pole pieces l4 and I5,

there are enerated currents corresponding to the Waves affecting themember 9. These cur- 'rents may be taken off by means of the lead wiresl2 and I3 and connected to suitable amplifying and/or currenttransmitting devices. On

the other hand, when the device is to be used as a sound reproducer thesoundcurrents are applied to the lead-wires I2 and I3 causingcorresponding electric fields to beset ;up in and around the member 9,and resulting incorresponding vibrations of this member.

It has'been found that by means of the'damping plate H the response ofthe device may be varied as desired. For example the elastic restoringforce of the vibratory system is a function 'ofthe'area of the member l1and its spacing relative tothe member 9. Secondly, by varying thislatter spacing theinherent restoring force of the system, andconsequently the resistance thereof may be accurately varied.

It will be understood of course that the invention is not limited to theuse of this air damping to control the response of the device. Forexample, the member 9 may be subjected to any desired tension so as tocontrol its actual period of vibration. However, as above describedpreferably the member 9 is designed and maintained so as to vibrate in asubstantially piston like manner. The restoring forces or elasticity ofthe vibrating system being substantially entirely provided by the airspace between the member 9 and the member ll. It is to be noted thatsince the member i! isof less width than the vibratory 'member 9 theimpinging sound waves strike the latter member directly, and thereis noreflection response in any portion of the useful range of the device.

It will be understood that various changes and modifications may be madeherein without departingfrom the spirit and. scope of the invention,.andwhile particular materials have been specified the inventionis notlimited thereto. For example, the member 9 may be treated or formed toimpart to it the necessary or required elasticity and/orrigidity.Likewise, this member instead of being made in the form of a continuousstrip maybe perforated or otherwise formed to control its actual periodof vibration. Likewise, the packing strip I1 may be formed or perforatedto control the responseof the device, and if desired the member I! maybe adjusted not only to vary the distance between it andthe it and thepole pieces I4 and l5.

. It will be understood of course that instead of employing permanentmagnets for magnetically energizing the device, any well known form of;

and a backing plate mounted in spaced relation 4. A device of thecharacter described comprising a pair of pole pieces defining a magneticgap in the form of a rectangularslit, a rectangular strip of conductive,material mounted in 7 said gap with the edges of the strip in spaced Irelation to the opposing edges of said pole pieces, a. backing strip,and means for adjusting the spacing between said ribbon member and saidbacking strip. I

5. A device according to claim 4 in which the backing strip issubstantially co-extensive in length with the ribbon member, butis of.lesser width to provide deferent passages for the air in back of saidribbon member. I

6. In a device of the character described the diaphragm, a damping platemounted in spaced relation to said diaphragm and to said pole pieces,and means for avoiding undesired resonance in the air space in back ofsaid diaphragm and damping plate.

ALEXANDER I. ABRAHAMS.

